Hermetic high-current therminal for electronic devices

ABSTRACT

A metallic conductor extends through an insulating material disposed in an opening of a sleeve and has an expansion coefficient closely matching that of the insulating material. A relatively thick copper layer is disposed only on the outer end portions of the conductor.

United States Patent Oates [4 1 Jan. 25,1972

[54] HERMETIC HIGH-CURRENT 2,377,164 5/1945 THERMINAL FOR ELECTRONIC232? 5:32; DEVICES 2,524,263 10/1950 [72] Inventor: William Lee Oates,Bernardsville, NJ. 2,835,826 Grieve at al l /1 2 M UX [73] Assignee: RCACorporation FOREIGN PATENTS OR APPLICATIONS [22] Filed: Mar- 10, 19912,115 5/1954 Germany ..174/152 GM [21] Appl' No; l22672 PrimaryExaminer-Laramie E. Askin Attorney-G. H. Brucstle [52] US. Cl ..174/l52GM,174/50.61, 287/189.365 [51] Int. Cl. ..H0lb 17/26 [57] ABSTRACT [58]Field of A metallic conductor extends through an insulating material287/189 3l3'/281 332 3 i 318 2 disposed in an opening ofa sleeve and hasan expansion coeffi- T l45D 145 T cient closely matching that of theinsulating material. A relatively thick copper layer is disposed only onthe outer end por- [5 References Cited tions of the conductor.

UNITED STATES PATENTS 6 Claims 2 Drawing 1,265,665 5/1918 Jacoby..287/l89.365

PATENTEDJANZSIBYZ 3.6375917 I N VENTOR.

M11151); L. Oates BY 11 TTOfP/VF Y HERMETIC HIGH-CURRENT THERMINAL FORELECTRONIC DEVICES BACKGROUND OF THE INVENTION The present inventionrelates to electronic devices, and in particular, relates tohigh-current terminal means for such devices.

A wide variety of high-current terminals are presently used in theelectronics industry. Many of these terminals are alike, however, inthat a metallic conductor extends through an insulating material, asglass, which fills an opening in a sleeve, or package header. Becausesuch terminals are generally required to operate at relatively hightemperatures, the metals selected for the conductor generally have athermal expansion coefficient closely matching that of the insulatingmaterial; to this end, Kovar and No. 52 alloy (52 percent nickel,balance iron) are frequently used.

However, these metals suffer relatively poor current-handlingcapabilities; thus, they are often combined with highly conductivemetals which are otherwise thermally mismatched with the insulatingmaterial. In one example, the conductor has a small copper core with athermally matched sheath surrounding the core. Yet another terminalemploys a relatively large thermally matching core, with a thin coppersheet completely surrounding the thermally matched metal. But these andother terminals still suffer thermal matching and current handlingcapabilities.

Another terminal, not rated for high-current use, is employed inradiofrequency devices. This terminal has a conductor of a thermallymatching metal extending through the insulating material. The outerportions of the conductor are plated with a very thin layer of a noblemetal, such as gold or silver, in order to improve the skin conductivityof the terminal. However, such RF terminals are not capable ofhigh-current operation as are other prior art terminals, such as thosedescribed above.

SUMMARY OF THE INVENTION The high-current terminal of the presentinvention comprises a sleeve member having two opposed surfaces with anopening between the surfaces, and with the opening filled with aninsulating material. A metallic conductor extends through the insulatingmaterial and has end portions which extend away from each of thesurfaces. The conductor has a coefficient of thermal expansion closelymatching that of the insulating material. A relatively thick copperlayer is disposed only on the end portions of the conductor.

THE DRAWING FIG. 1 is a cross-sectional view of the high-currentterminal of the present invention.

FIG. 2 is a cross-sectional front view of the terminal of FIG. 1, takenalong the lines 2-2.

DETAILED DESCRIPTION The high-current terminal of the present inventionwill be described with reference to FIGS. 1 and 2. The terminal,referred to generally as 10, includes a metal sleeve member 12 havingopposed front and back surfaces 13 and 15, respectively, with an opening14 between the two surfaces. The dimensions of the sleeve member 12 arenot critical. By way of example, the sleeve member may be 0.10 inchthick between the two surfaces 13 and 15, and the opening 14 may bebetween 0.07 and 0.09 inch in diameter.

An insulating material 16 fills the opening 14. Preferably, theinsulating material comprises a glass such as Corning Standard numbers7052 or 9010, which glasses have thermal expansion coefficients of 4610"'/in./ C. and 89Xl0"/in./ C., respectively. A metallic conductor 18extends through and is sealed to the insulating material. The conductor18 has a thermal expansion coefficient which closely matches that of theinsulating material 16. Preferably, the conductor comprises Kovar or No.52 alloy, which metals have thermal expansion coefficients of50X10"/in./ C. and 101 Xl0"/in./ C., respectively. The conductor may bebetween 20.0 and 30.0 mils in radius, for example.

The conductor 18 also includes end portions 20 and 22 which extend awayfrom the two surfaces of the sleeve 13 and 15, respectively. The endportions 20 and 22 are coated with a relatively thick copper layer 24.Noting FIG. 2, the thermally matched conductor 18 defines a first radiusr,, and the outer periphery of the copper layer 24 defines a secondradius r,, which shares a common origin with the first radius r In orderthat the terminal 10 can achieve an optimum current handling capability,it is preferable that radius r, be at least 10.0 percent greater thanradius r,. Thus, if radius r, is 20.0 mils, then radius r is at least 22mils, and preferably about 25.0 mils. Since the thermally matchedconductor 18 will not normally have a radius (r less that 20.0 mils,then the term relatively thick" is intended to mean that the copperlayer 24 is at least 2.0 mils thick, and preferably about 4.0 mils orthicker.

The sleeve member 12 may also have a relatively thick copper layer 26deposited on the exposed surface thereof, which copper layer 26 isdeposited on the sleeve member 12, during the preferred fabrication ofthe terminal 10, as described below. The terminal 10 is joined to anelectronic device package header 28.

The metal conductor 18 may be sealed in the insulating material 16, andthe insulating material may be disposed in the opening 14 of the sleeve12, by fabrication techniques which are well known in the art. Therelatively thick copper layer 24 may be deposited by any one of avariety of plating processes; for example, any electrolytic orelectroless plating process. In addition, during the deposition of thecopper layer 24, the copper layer 26 on the sleeve 12 is deposited toprovide additional heat dissipation capability.

The terminal 10 of the present invention provides a good thermalexpansion matching between the metal conductor 18 and the insulatingmaterial 16. In addition, the relatively thick copper layer which isdisposed only on those portions 20 and 22 of the conductor 18 outside ofthe insulating material 16 provides a very high-current carryingcapability; for example, a 5.0 mil copper layer on a 40.0 mil thermallymatched conductor has about twice the current-handling capability of the40.0 mil thermally matched conductor alone.

What is claimed is:

l. A high-current terminal comprising:

a sleeve member having two opposed surfaces and an opening between saidsurfaces;

an insulating material in said opening;

a metallic conductor extending through said insulating material with endportions extending away from each said surface, said conductor having acoefficient of thermal expansion closely matching that of saidinsulating material; and

a relatively thick copper layer disposed only on said end portions ofsaid conductor.

2. A terminal according to claim 1 wherein said insulating materialcomprises glass.

3. A terminal according to claim 2 wherein said metallic conductorcomprises an iron-nickel-cobalt alloy.

4. A terminal according to claim 2 wherein said metallic conductorcomprises 52 percent nickel, balance iron.

5. A terminal according to claim 1 wherein said copper layer is at least3.0 mils thick.

6. A high-current terminal comprising:

a sleeve member having two opposed surfaces with an opening between saidsurfaces;

an insulating material in said opening;

a cylindrical metallic conductor having a first radius extending throughsaid insulating material with end portions extending away from each saidsurface, said conductor having a coefficient of thermal expansionclosely matching that of said insulating material;

a uniform copper layer disposed only on said end portions of saidconductor, the outer periphery of said copper layer defining a secondradius having a common origin with said first radius; and wherein saidsecond radius is at least 10.0 percent greater than said 5 first radius.

1. A high-current terminal comprising: a sleeve member having twoopposed surfaces and an opening between said surfaces; an insulatingmaterial in said opening; a metallic conductor extending through saidinsulating material with end portions extending away from each saidsurface, said conductor having a coefficient of thermal expansionclosely matching that of said insulating material; and a relativelythick copper layer disposed only on said end portions of said conductor.2. A terminal aCcording to claim 1 wherein said insulating materialcomprises glass.
 3. A terminal according to claim 2 wherein saidmetallic conductor comprises an iron-nickel-cobalt alloy.
 4. A terminalaccording to claim 2 wherein said metallic conductor comprises 52percent nickel, balance iron.
 5. A terminal according to claim 1 whereinsaid copper layer is at least 3.0 mils thick.
 6. A high-current terminalcomprising: a sleeve member having two opposed surfaces with an openingbetween said surfaces; an insulating material in said opening; acylindrical metallic conductor having a first radius extending throughsaid insulating material with end portions extending away from each saidsurface, said conductor having a coefficient of thermal expansionclosely matching that of said insulating material; a uniform copperlayer disposed only on said end portions of said conductor, the outerperiphery of said copper layer defining a second radius having a commonorigin with said first radius; and wherein said second radius is atleast 10.0 percent greater than said first radius.